TY - JOUR A1 - Einhorn-Stoll, U. A1 - Benthin, A. A1 - Zimathies, Annett A1 - Görke, O. A1 - Drusch, S. T1 - Pectin-water interactions: comparison of different analytical methods and influence of storage N2 - Interactions of pectin with water are essential for nearly all pectin applications. It was assumed that these interactions strongly depend not only on chemical molecular parameters but also on physical powder material properties and that they might be affected by storage. This was examined with nine different pectin samples from three suppliers. Storage at 60 °C and 80% humidity for two weeks was used in order to simulate long term storage at moderate conditions. Material properties were tested by measuring solid density and BET surface and by mercury porosimetry and X-ray analysis. Pectin-water interactions were examined with two different methods, a modified sorption method at αw around 1.0 and the capillary sucking method (Baumann method). After storage, the BET surface of the pectin samples was reduced, solid density was altered differently and crystalline structures became amorphous. It is assumed that storage at high heat and humidity caused particle surfaces softening, swelling and partly dissolution. The particle surfaces smoothed, small inter-particle voids were reduced or sealed and particles agglomerated. These alterations caused a reduced water uptake of stored pectins. In general, the accessibility of hydrophilic groups in pectin was more important for pectin-water interactions than their number. All applied methods for testing pectin-water interactions detected special sample properties and their combination allowed an extensive evaluation of the water binding properties. KW - Pectin KW - Material properties KW - Water binding KW - Storage PY - 2015 U6 - https://doi.org/10.1016/j.foodhyd.2014.07.013 SN - 0268-005X VL - 43 SP - 577 EP - 583 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-31634 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Einhorn-Stoll, U. A1 - Kastner, H. A1 - Hecht, T. A1 - Zimathies, Annett A1 - Drusch, S. T1 - Modification and physico-chemical properties of citrus pectin - Influence of enzymatic and acidic demethoxylation N2 - Aim of the present study was to investigate the effect of the method of demethoxylation on the particle structure and techno-functional properties of pectins with different degree of methoxylation and distribution of free carboxyl groups. Two groups of model pectins, one with 57% and one with 42% degree of methoxylation have been prepared from one single commercial pectin. Modifications were performed by an acidic and two enzymatic methods using fungal and plant-derived pectin methyl esterases. Thermal stability was investigated by thermal analysis and water uptake was determined by a sorption and a capillary sucking method. The enzyme-treated pectins were thermally less stable than the acid-treated. The water uptake of enzyme-treated pectins was higher than in acid-treated samples in the sorption method and lower in the capillary sucking tests. The different behaviour is explained by differences in pH during demethoxylation and a co-occurring variation in sodium content. Both parameters affected intermolecular interactions of the pectin macromolecules in solution, which resulted in differences in the particle morphology. The effect of the distribution of free carboxyl groups (statistical or block-wise) on the techno-functional properties was more pronounced in high-methoxylated pectins than in low-methoxylated pectins. KW - Pectin KW - Demethoxylation KW - PH-influence KW - Thermal stability KW - Water sorption PY - 2015 U6 - https://doi.org/10.1016/j.foodhyd.2015.05.031 SN - 0268-005X VL - 51 SP - 338 EP - 345 PB - Elsevier Science CY - Amsterdam [u.a.] AN - OPUS4-33616 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -